Drive mechanism for a drug delivery device

ABSTRACT

The present invention relates to a drive mechanism of a drug delivery device for dispensing of a dose of a medicament, the mechanism comprising: an elongated housing (20) extending in an axial direction (1, 2), a piston rod (160) to operably engage with a piston (14) of a cartridge (12) to displace the piston (14) in axial distal direction (1), a dose setting member (120; 220) rotatably arranged at a proximal end of the housing (20) for setting of a dose, a base member (60; 260) having a proximally extending shaft portion (61; 261) at least partially enclosed by the dose setting member (120; 220), a last dose limiting member (140; 240) radially disposed between the dose setting member (120; 220) and the base member (60; 260) and having at least one radial stop (143; 243a, 243b) to limit a rotational displacement of the dose setting member (120; 220) relative to the base member (60; 260), wherein the last dose limiting member (140; 240) is rotatably locked but axially displaceable to one of the base member (60; 260) and the dose setting member (120; 220) and wherein the last dose limiting member (140; 240) is threadedly engaged with the other one of the base member (60; 260) and the dose setting member (120; 220).

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a U.S. National Phase Application pursuant to 35 U.S.C. § 371 of International Application No. PCT/EP2014/057003 filed Apr. 8, 2014, which claims priority to European Patent Application No. 13163112.9 filed Apr. 10, 2013. The entire disclosure contents of these applications are herewith incorporated by reference into the present application.

The present invention relates to a drive mechanism for a drug delivery device and to a respective drug delivery device. In particular, the invention relates to an injection device such like a pen-type injector inter alia comprising a single and/or a last-dose limiting mechanism.

BACKGROUND AND PRIOR ART

Drug delivery devices for setting and dispensing a single or multiple doses of a liquid medicament are as such well-known in the art. Generally, such devices have substantially a similar purpose as that of an ordinary syringe.

Drug delivery devices, in particular pen-type injectors have to meet a number of user-specific requirements. For instance, with patient's suffering chronic diseases, such like diabetes, the patient may be physically infirm and may also have impaired vision. Suitable drug delivery devices especially intended for home medication therefore need to be robust in construction and should be easy to use. Furthermore, manipulation and general handling of the device and its components should be intelligible and easy understandable. Moreover, a dose setting as well as a dose dispensing procedure must be easy to operate and has to be unambiguous.

Typically, such devices comprise a housing or a particular cartridge holder, adapted to receive a cartridge at least partially filled with the medicament to be dispensed. The device further comprises a drive mechanism, usually having a displaceable piston rod which is adapted to operably engage with a piston of the cartridge. By means of the drive mechanism and its piston rod, the piston of the cartridge is displaceable in a distal or dispensing direction and may therefore expel a predefined amount of the medicament via a piercing assembly, which is to be releasably coupled with a distal end section of the housing of the drug delivery device.

The medicament to be dispensed by the drug delivery device is provided and contained in a multi-dose cartridge. Such cartridges typically comprise a vitreous barrel sealed in distal direction by means of a pierceable seal and being further sealed in proximal direction by the piston. With reusable drug delivery devices an empty cartridge is replaceable by a new one. In contrast to that, drug delivery devices of disposable type are to be entirely discarded when the medicament in the cartridge has been completely dispensed or used-up.

With such multi-dose drug delivery devices at least a last dose limiting mechanism is required to inhibit setting of a dose exceeding the amount of medicament left in the cartridge. This is to avoid a potentially dangerous situation for the user believing that a set dose is entirely injected.

There already exist some drug delivery devices with end-of-content mechanisms or last dose mechanisms.

Document WO 2004/007003 A1 for instance discloses an end-of-content arrangement for preventing a dose setting member of an injection device to be set to a dose larger than the medicament remaining in the injection device. There is described a dose setting and injecting mechanism featuring an arm flexibly hinged to a coupling ring. Said arm is equipped with a cam engaging a spiral-shaped track provided on a driver. When a dose setting member and the coupling ring is rotated in a clockwise direction during the setting of a dose, the cam on the arm is moved along the track in an outward direction whereas the cam, during injection, due to the concomitant rotation of the coupling ring and the driver remains in its position in the track obtained during the dose setting.

The length of the spiral track is synchronised with the content in the cartridge such that the cam is guided out through the track opening when the cartridge is almost empty.

With many of these known approaches the last dose limiting mechanism is located rather remote from an actuation member, such like a dose dial member, by way of which the user may interact with the drive mechanism, e.g. for setting and/or dispensing of a dose. For limiting or delimiting a dose setting procedure, the angular momentum or driving force exerted by a user of the device has to be transferred from the actuation member almost through the entire drive mechanism and the plurality of its mutually interacting components until the last dose limiting mechanism is eventually activated and blocks a further dose incrementing movement of the drive mechanism and of its various components.

Since the mechanically interacting components of a drive mechanism are always subject to inevitable mechanical tolerances, a respective tolerance chain extending between the actuation member, e.g. a dose dial, and the last dose limiting mechanism may be fairly long. In effect, once a last dose limiting mechanism is activated and actually inhibits a dose incrementing displacement of e.g. a drive sleeve relative to a housing or relative to a piston rod, the locking or blocking of e.g. the drive sleeve has to propagate and to be transferred or returned to the dose dial member. Also here, due to the tolerance chain at least a minimal displacement, e.g. a rotation of the dose dial member may still be possible even though a dose incrementing displacement of the drive mechanism is effectively blocked.

It is therefore an object of the present invention to avoid disadvantages of known drug delivery devices and to provide a drive mechanism for a drug delivery device allowing for an intuitive operation, both for setting and for dispensing of a dose.

It is another object of the present invention to provide a drive mechanism for a drug delivery device for setting and dispensing of a dose of a medicament typically provided in a cartridge, wherein the drive mechanism is equipped with a last dose limiting mechanism. The last dose limiting mechanism should be rather precise and robust and should be easy to implement in the drive mechanism. The last dose limiting mechanism should further provide an immediate and an almost backlash-free feedback to the user when setting of a dose exceeding the amount of medicament left in the cartridge.

It is a further object to provide a drug delivery device featuring an improved last dose limiting mechanism.

SUMMARY OF THE INVENTION

In a first aspect a drive mechanism for a drug delivery device is provided for dispensing of a dose of a medicament. The drive mechanism comprises an elongated housing extending in an axial direction. Typically, the housing is of substantially tubular or cylindrical shape that allows and supports gripping and operating of the drive mechanism or of the entire drug delivery device by one hand of a user.

The drive mechanism further comprises a piston rod to operably engage with a piston of a cartridge containing the medicament to be dispensed by the drive mechanism. The cartridge comprises a piston, which, by means of a displacement in axial distal direction, serves to expel an amount of the medicament from the cartridge. Said expelled or dispensed amount correlates to the axial displacement of the piston as determined by the respective axially-directed displacement of the drive mechanism's piston rod.

Typically, the piston seals the cartridge in axial proximal direction. The piston rod of the drive mechanism serves to displace the piston of the cartridge in the axial direction. The piston rod is therefore operable to apply distally-directed thrust or pressure to the piston of the cartridge for displacing the same in distal direction for a predetermined distance that corresponds to the respective amount of the medicament, hence to the dose of the medicament to be dispensed.

Furthermore, the drive mechanism comprises a dose setting member rotatably arranged at a proximal end of the housing for setting of a dose. The dose setting member typically comprising a sleeve-like geometry can be dialled by a user of the device at least in a dose incrementing direction for increasing the size of the dose to be set. Typically, the dose setting member is rotatably engaged with a drive sleeve of the drive mechanism. The drive sleeve may be engaged with a spring element so that a dose incrementing rotation of the drive sleeve and hence of the dose setting member strains the spring element for storing mechanical energy.

In this way, the dose setting member not only serves to set or to select a dose of variable size but also serves to increase a dose size against the action of a spring element. In a subsequent dose dispensing procedure, mechanical energy stored in the spring element may be used to drive at least the drive sleeve in an opposite direction, hence in a dose decrementing direction. When the drive sleeve is driven by the relaxing spring element, its rotational movement is typically transferred into a distally directed displacement of the piston rod for driving the piston of the cartridge in distal direction for expelling a dose of the medicament therefrom.

The drive mechanism further comprises a base member having a proximally extending shaft portion at least partially enclosed by the dose setting member. The base member may be integrally formed with the elongated housing and may form a proximal end of the housing. Alternatively, the base member may be provided as a separate part to be fixedly assembled in or to the housing. In either way, the base member provides a mechanical support as well as a kind of a bearing for the rotatable dose setting member.

Additionally, the drive mechanism comprises a last dose limiting member radially disposed between the dose setting member and the base member. The last dose limiting member further has at least one radial stop to limit a rotational displacement of the dose setting member relative to the base member. The at least one radial stop is adapted to engage with a corresponding radial stop of the base member. When the mentioned stops of the last dose limiting member and the dose setting member mutually engage, a further dose incrementing rotation of the dose setting member is substantially blocked.

Typically, such a blocked or internal locking configuration is obtained when an end of content configuration of the cartridge has been reached, which typically correlates to a maximum distal position of the piston rod.

The last dose limiting member is rotatably locked but axially displaceable to one of the base member and the dose setting member. The last dose limiting member is further threadedly engaged with the other one of the base member and the dose setting member. In this way, the last dose limiting member is splined with one of base member and dose setting member but is threadedly engaged with the other one of base member and dose setting member.

For instance, the last dose limiting member is rotatably locked to the dose setting member and is threadedly engaged with the base member. Then, a rotation of the dose setting member relative to the base member equally transfers to a rotation of the last dose limiting member. Due to its threaded engagement with the base member, the last dose limiting member travels in axial direction relative to the base member and hence relative to the dose setting member, since the dose setting member is axially fixed to the base member.

Rotational interlocking of the dose setting member and the last dose limiting member may be provided by at least one radially extending protrusion and a correspondingly shaped recess of the dose setting member and the last dose limiting member. For instance, the dose setting member may comprise an axially extending radial groove in which a radially outwardly extending protrusion of the last dose limiting member extends. Since protrusion and recess mutually match, a rotation of the dose setting member equally and unalterably transfers to a respective rotation of the last dose limiting member.

Moreover, since the recess of e.g. the dose setting member engaging with the radial protrusion of the last dose limiting member extends in axial direction, the last dose limiting member may travel in axial direction relative to the dose setting member according to the lead of the mutually corresponding threads of the last dose limiting member and the shaft portion of the base member to which the last dose limiting member is mounted.

In an alternative embodiment it is the base member, in particular its shaft portion that features a recessed or radially protruding structure to engage with a correspondingly shaped protruding structure or recess of the last dose limiting member. Here, the last dose limiting member may comprise a radially inwardly extending protrusion engaged with a radially inwardly extending recess of the base member's shaft portion extending in axial direction. Additionally, the last dose limiting member may then comprise an outer thread to threadedly engage with an inner threaded portion of the dose setting member. In this way, a rotation of the dose setting member also leads to an axial displacement of the last dose limiting member along the recessed structure of the base member's shaft portion.

In either embodiment, the last dose limiting member is adapted to block a rotation of the dose setting member as soon as a last dose limiting configuration of the drive mechanism has been reached.

Since the last dose limiting member is directly engaged with the rotatable dose setting member, a rather direct and unaltered feedback can be provided to the user as soon as the last dose limiting configuration has been reached.

By directly engaging the last dose limiting member with the dose setting member, a rather unaltered and immediate feedback can be given to the user when the last dose limiting configuration and hence a blocking of the dose setting member has been reached. Due to the direct mutual engagement of the last dose limiting member and the dose setting member, the last dose limiting mechanism is almost free of backlash or mechanical play between the various components of the drive mechanism.

According to another embodiment, the last dose limiting member comprises a radial protrusion or a radial and axially extending recess engaged with a correspondingly shaped radial and axially extending recess of the dose setting member or base member. In either way, the last dose limiting member may rotatably engage or may be rotatably locked to either the dose setting member or to the base member while being threadedly engaged to the other one of the dose setting member or the base member.

In either way, rotation of the dose setting member then leads to an axial displacement of the last dose limiting member until a last dose stop configuration is reached.

According to another embodiment, the last dose limiting member comprises a radially outwardly extending protrusion extending into or through a radial recess of the dose setting member. Moreover, the dose limiting member comprises an inner thread engaged with an outer thread of the base member. By means of the radially outwardly extending protrusion extending into or through a radial recess of the dose setting member, a rotational interlock or rotational engagement of the last dose limiting member with the dose setting member can be obtained.

Typically, the radial recess of the dose setting member resembles or comprises an axially extending slot, in which the radially outwardly extending protrusion of the last dose limiting member may travel as the last dose limiting member is rotated along the outer thread of the base member's threaded shaft portion.

Having the last dose limiting member threadedly engaged with the shaft portion of the base member allows for a particularly easy assembly of dose setting member, base member and last dose limiting member sandwiched therebetween. In particular, the sleeve like or cup-shaped dose setting member may be clipped onto the base member by inserting the radially outwardly extending protrusion of the last dose limiting member into the correspondingly shaped radial recess of the dose setting member and by displacing the dose setting member into its final assembly configuration, in which it may snap fit with the base member in such a way, that the dose setting member is axially fixed to the base member or to a respective housing of the drive mechanism.

In still another embodiment, the last dose limiting member comprises an annular structure. In particular, when the annular structure is a closed annular structure the radial stop of the last dose limiting member extends in axial direction from said annular structure to engage with a correspondingly shaped radial stop of the dose setting member. A radial stop comprises a stop face extending in radial and axial direction. In this way, an immediate blocking of two corresponding radial stops can be obtained as soon as the two stop faces mutually hit.

In embodiments, wherein the last dose limiting member is threadedly engaged and is hence rotatable relative to the dose setting member, it is the dose setting member that comprises a radial stop correspondingly shaped and arranged to the radial stop of the last dose limiting member.

The last dose limiting member may also comprise a second radial stop, by way of which the last dose limiting member may engage with a correspondingly shaped stop face of the dose setting member in an initial configuration that corresponds to a zero dose configuration.

Such a second stop configuration may be useful for preventing setting of a negative dose when the drive mechanism is used for the first time.

In another embodiment, the last dose limiting member is arc shaped and may comprise a semi-circular structure. Here, radial stops may be located at circumferential end faces of the last dose limiting member. Such a configuration may be beneficial for mounting the last dose limiting member to the shaft portion of the base member. The semi-circular shape may allow for a radially directed mounting of the last dose limiting member to the base member.

According to another embodiment, the drive mechanism comprises a dose setting sleeve rotatably and axially connected with a drive sleeve and being axially displaceable between a proximal dose setting position and a distal dose dispensing position. In the proximal dose setting position, the dose setting sleeve and hence the drive sleeve is rotatably locked or rotatably engaged with the dose setting member. In this way, a dose incrementing but also a dose decrementing rotation of the dose setting member relative to the housing or relative to the base member equally transfers to a corresponding rotational displacement of the dose setting sleeve and the drive sleeve.

Since the drive sleeve is engaged with the housing via a spring element, the drive sleeve may be rotated in a dose incrementing direction against the action of said spring element. Typically, the spring element surrounds and extends along at least a portion of the drive sleeve. The spring element may comprise a helical shape and may act as a torsion spring. If the drive sleeve and hence the dose setting sleeve is axially displaced into the distal dose dispensing position the drive sleeve and/or the dose setting sleeve are free to rotate under the action of the biased spring element.

Moreover, in the distal dose dispensing position the drive sleeve is further rotatably coupled or rotatably engaged with a drive wheel and hence with the piston rod for driving the same in distal direction for dispensing of a dose of the medicament.

According to another embodiment the dose setting member is rotatably engaged with the dose setting sleeve when in dose setting position. Additionally, the dose setting member is rotatably disengaged from the dose setting sleeve when the dose setting member is in dose dispensing position. In this way, and by the selected rotational engagement of the dose setting member and the dose setting sleeve, a rotation of the dose setting member for either incrementing or decrementing of a dose is only effective when the dose setting sleeve is in its proximal dose setting position.

During dose dispensing and when axially displaced in distal direction towards and into the distal dose dispensing position, the dose setting sleeve is effectively decoupled from the dose setting member and may therefore freely rotate under the action of the relaxing spring element. Consequently, the dose setting member will not be driven by the dose setting sleeve rotating in a dose decrementing direction. During a dose dispensing procedure it is particularly intended that the dose setting member is rotatably locked to the housing or to the base member in order to inhibit any further rotation of the dose setting member.

According to another embodiment the drive mechanism further comprises a dose dispensing member arranged at a proximal end of the dose setting member and being depressible in distal direction for displacing the dose setting sleeve in the dose dispensing position. The dose dispensing member may comprise a cup-like shape and may form a proximal end face of the drive mechanism or of the entire drug delivery device. The dose dispensing member may effectively serve as a dose button to be depressed in distal direction for initiating and for controlling a dose dispensing procedure.

Typically, the dose dispensing member is depressible in distal direction against the action of a retention spring. In this way, the dose dispensing member may be axially displaceable relative to the dose setting member. For this purpose, the dose dispensing member and/or the dose setting member may comprise at least one spring element, by way of which the dose dispensing member may return into a proximal end configuration as soon as a user no longer depresses the dose dispensing member.

In still another embodiment the dose dispensing member comprises an axially extending shaft portion extending from a proximal end face thereof in distal direction. The distally extending shaft portion pointing towards the interior of the drive mechanism is particularly adapted to axially abut with the dose setting sleeve. It is the distally extending shaft portion of the dose dispensing member, by way of which a distally directed axial displacement of the dose dispensing member may be equally transferred to a corresponding distally directed displacement of the dose setting sleeve.

The dose setting sleeve and/or the drive sleeve rigidly interconnected therewith may be axially supported in the housing by means of a retention spring element. In this way, the dose setting sleeve may be axially displaced in distal direction against the action of the retention spring element. Consequently, keeping the dose setting sleeve as well as the drive sleeve in their distally located dose dispensing position requires constant application of a distally directed depressing force acting on the dose dispensing member.

In the event that a user releases the dose dispensing member, the dose dispensing member as well as the dose setting sleeve and the drive sleeve may be immediately displaced in proximal direction under the action of the retention spring and may return into the proximal dose setting position, in which the drive sleeve is operably disengaged from the piston rod.

Since dose dispensing member and the dose setting sleeve are axially displaceable in distal direction against the action of the retention spring element, the dose dispensing member not only serves to trigger but also to control a dose dispensing procedure. In the event that a user intends to interrupt a dose dispensing procedure he may simply release the dose dispensing member. Due to the at least one retention spring element the drive sleeve and hence the dose setting sleeve immediately return into their dose setting position in which the drive sleeve is operably decoupled and disengaged from the piston rod.

According to another embodiment the dose setting member and the dose dispensing member are rotatably engaged by means of at least one radially inwardly extending protrusion of the dose setting member. Said radially inwardly extending protrusion of the dose setting member extends through an axially extending slot of the dose dispensing member. In this way, dose setting member and dose dispensing member are permanently rotatably coupled. Additionally, the axially extending slot of the dose dispensing member allows to arrange the dose setting member and the dose dispensing member in a nested and radially overlapping configuration. Here, the dose dispensing member having the axially extending slot extending in a sidewall portion thereof may extend into the sleeve like shape of the dose setting member.

In another embodiment the dose dispensing member is rotatably locked to the base member or to the housing when distally displaced or when located in the distal dose dispensing position. Since dose dispensing member and dose setting member are permanently rotatably locked, the mechanical engagement of the dose dispensing member with the base member or with the housing in the dose dispensing position also rotatably locks the dose setting member to the housing. In this way, the dose dispensing member is effectively blocked and may not be rotated in any direction as soon as the dose dispensing member is depressed in dose dispensing position.

The interlocking of the dose setting member with the base member or with the housing during dose dispensing is of particular importance since the last dose limiting member is then also immobilized and fixed relative to the base member. In this way, the axial position of the last dose limiting member always reflects the total distance the piston rod has advanced in distal direction during consecutive dose setting and dose dispensing procedures. Hence, the dose dispensing history, at least the total amount of medicament dispensed from the cartridge is reflected in the axial position of the last dose limiting member relative to the base member and/or relative to the dose setting member.

Moreover, said interlocking is also beneficial in terms of user or patient safety. By either directly or indirectly engaging the dose setting member with the base member and/or with the housing during a dose setting procedure, the user is hindered to modify the previously set size of the dose. Otherwise, if the dose setting member would not be interlocked during dose dispensing a user could manipulate the position of the last dose limiting member by rotating the dose setting member while simultaneously depressing the dose dispensing member.

According to another embodiment, the dose setting sleeve is rotatably locked to the dose setting member when in dose setting position. In this way, a user-induced rotation of the dose setting member is equally and unalterably transferred to the dose setting sleeve and hence to the drive sleeve. Moreover, when the dose dispensing member and hence the dose setting sleeve are located in the distal dose dispensing position the dose setting sleeve is effectively decoupled and disengaged from the dose setting member.

In this way and during dose dispensing the dose setting member is locked to the housing or to the base member while the dose setting sleeve and hence the drive sleeve are liberated to rotate under the action of the relaxing spring element for driving the piston rod in distal direction.

According to another embodiment the dose setting member is rotatably locked to the base member or to the housing via the dose dispensing member when the dose dispensing member is in dose dispensing position. For this, the dose dispensing member comprises axially extending engaging means by way of which it may interlock with the base member when reaching the dose dispensing position. Here it may be of particular benefit when the distally extending shaft portion of the dose dispensing member rotatably engages or rotatably interlocks with the base member when reaching the distal dose dispensing position.

In this way, the axially and distally extending shaft portion of the dose dispensing member comprises a twofold or double function. On the one hand it serves to axially displace the dose setting sleeve in distal direction for disengaging the dose setting sleeve from the dose setting member and for engaging the dose setting sleeve and hence the drive sleeve with a drive wheel to exert a driving force to the piston rod. On the other hand, the distally extending shaft of the dose dispensing member may comprise a geared or toothed, hence a recessed or protruding structure at its outer circumference to rotatably engage with a correspondingly shaped portion of the base member when reaching the distally located dose dispensing position.

According to a further embodiment the dose setting member comprises at least two circumferentially separated but radially inwardly extending protrusions extended by at least one circumferentially extending arched portion. Said arched portion may extend substantially parallel but radially separated to the sidewall of the dose setting member. Hence, the arched portion may comprise a radius of curvature which is smaller than the radius of curvature of the sleeve-like outer sidewall portion of the dose setting member.

The difference in the radii of curvature may correspond to the radial extent of the radially inwardly extending protrusions interconnecting the arched portion with the inward facing sidewall portion of the dose setting member.

By means of the at least one circumferentially extending arched portion, the dose setting member may radially engage with the last dose limiting member of annular geometry. Hence, the last dose limiting member may serve as a guiding structure on which the dose setting member may be radially supported and rotated for setting of a dose. Typically, the dose setting member comprises at least two geometrically oppositely located radially inwardly extending protrusions and respective circumferentially extending arched portions so that a rather homogeneous and smooth radial support can be provided for the dose setting member.

In still another embodiment, the radial recess of the dose setting member, which is adapted to engage with a radially outwardly extending protrusion of the last dose limiting member is located in the arched portion or between adjacently located arched portions facing towards each other in circumferential direction.

Since the arched portions of the dose setting member are located radially inwardly and radially separated from the outer sidewall portion of the dose setting member, the recess to engage with the radially outwardly extending protrusion of the last dose limiting member may be designed as a through opening in the arched portion or as a complete gap between two separate arched portions. In this way, a rather large radial extent of the radially outwardly extending protrusion of the last dose limiting member can be implemented, thereby providing a rather robust and secure rotational interlock and rotational engagement with the dose setting member. By having the recessed structure provided in an inner arched portion of the dose setting member, the outer appearance of the dose setting member is substantially unaffected by this mutual radial engagement.

According to another aspect, the invention also relates to a drug delivery device for dispensing of a dose of a medicament. The drug delivery device comprises a drive mechanism as described above and a cartridge at least partially filled with the medicament to be dispensed by the drug delivery. The cartridge is arranged in the housing of the drive mechanism or in a cartridge holder of the drug delivery device which is fixed to the housing either releasably or non-releasably, e.g. in case of a disposable drug delivery device. Consequently, the drug delivery device comprises a cartridge holder to receive and to accommodate a cartridge filled with the medicament.

In the present context, the distal direction points in the direction of the dispensing and of the device, where, preferably a needle assembly is provided having a double-tipped injection needle that is to be inserted into biological tissue or into the skin of a patient for delivery of the medicament.

The proximal end or proximal direction denotes the end of the device or a component thereof, which is furthest away from the dispensing end. Typically, an actuating member is located at the proximal end of the drug delivery device, which is directly operable by a user to be rotated for setting of a dose and which is operable to be depressed in distal direction for dispensing of a dose.

The drive mechanism particularly serves to displace a piston rod in axial direction for the purpose of dispensing of a dose of a medicament. In addition, the drive mechanism typically comprises components which also form part of and have a function in at least one of the following mechanisms: a dose setting mechanism, a last dose limiting mechanism and a dose indicating mechanism. As will be apparent from the embodiments described herein various components of e.g. the drive mechanism also belong to at least one of the dose setting mechanism, the last dose limiting mechanism and/or to the dose indicating mechanism; and vice versa. Hence, the invention as described herein equally refers to and defines a drive mechanism, a dose setting mechanism, a last dose limiting mechanism and/or a dose indicating mechanism of a drug delivery device.

The term “drug” or “medicament”, as used herein, means a pharmaceutical formulation containing at least one pharmaceutically active compound,

wherein in one embodiment the pharmaceutically active compound has a molecular weight up to 1500 Da and/or is a peptide, a proteine, a polysaccharide, a vaccine, a DNA, a RNA, an enzyme, an antibody or a fragment thereof, a hormone or an oligonucleotide, or a mixture of the above-mentioned pharmaceutically active compound,

wherein in a further embodiment the pharmaceutically active compound is useful for the treatment and/or prophylaxis of diabetes mellitus or complications associated with diabetes mellitus such as diabetic retinopathy, thromboembolism disorders such as deep vein or pulmonary thromboembolism, acute coronary syndrome (ACS), angina, myocardial infarction, cancer, macular degeneration, inflammation, hay fever, atherosclerosis and/or rheumatoid arthritis,

wherein in a further embodiment the pharmaceutically active compound comprises at least one peptide for the treatment and/or prophylaxis of diabetes mellitus or complications associated with diabetes mellitus such as diabetic retinopathy,

wherein in a further embodiment the pharmaceutically active compound comprises at least one human insulin or a human insulin analogue or derivative, glucagon-like peptide (GLP-1) or an analogue or derivative thereof, or exendin-3 or exendin-4 or an analogue or derivative of exendin-3 or exendin-4.

Insulin analogues are for example Gly(A21), Arg(B31), Arg(B32) human insulin; Lys(B3), Glu(B29) human insulin; Lys(B28), Pro(B29) human insulin; Asp(B28) human insulin; human insulin, wherein proline in position B28 is replaced by Asp, Lys, Leu, Val or Ala and wherein in position B29 Lys may be replaced by Pro; Ala(B26) human insulin; Des(B28-B30) human insulin; Des(B27) human insulin and Des(B30) human insulin.

Insulin derivates are for example B29-N-myristoyl-des(B30) human insulin; B29-N-palmitoyl-des(B30) human insulin; B29-N-myristoyl human insulin; B29-N-palmitoyl human insulin; B28-N-myristoyl LysB28ProB29 human insulin; B28-N-palmitoyl-LysB28ProB29 human insulin; B30-N-myristoyl-ThrB29LysB30 human insulin; B30-N-palmitoyl- ThrB29LysB30 human insulin; B29-N-(N-palmitoyl-Y-glutamyl)-des(B30) human insulin; B29-N-(N-lithocholyl-Y-glutamyl)-des(B30) human insulin; B29-N-(ω-carboxyheptadecanoyl)-des(B30) human insulin and B29-N-(ω-carboxyhepta-decanoyl) human insulin.

Exendin-4 for example means Exendin-4(1-39), a peptide of the sequence H His-Gly-Glu-Gly-Thr-Phe-Thr-Ser-Asp-Leu-Ser-Lys-Gln-Met-Glu-Glu-Glu-Ala-Val-Arg-Leu-Phe-Ile-Glu-Trp-Leu-Lys-Asn-Gly-Gly-Pro-Ser-Ser-Gly-Ala-Pro-Pro-Pro-Ser-NH2.

Exendin-4 derivatives are for example selected from the following list of compounds:

-   H-(Lys)4-des Pro36, des Pro37 Exendin-4(1-39)-NH2, -   H-(Lys)5-des Pro36, des Pro37 Exendin-4(1-39)-NH2, -   des Pro36 Exendin-4(1-39), -   des Pro36 [Asp28] Exendin-4(1-39), -   des Pro36 [IsoAsp28] Exendin-4(1-39), -   des Pro36 [Met(O)14, Asp28] Exendin-4(1-39), -   des Pro36 [Met(O)14, IsoAsp28] Exendin-4(1-39), -   des Pro36 [Trp(O2)25, Asp28] Exendin-4(1-39), -   des Pro36 [Trp(O2)25, IsoAsp28] Exendin-4(1-39), -   des Pro36 [Met(O)14 Trp(O2)25, Asp28] Exendin-4(1-39), -   des Pro36 [Met(O)14 Trp(O2)25, IsoAsp28] Exendin-4(1-39); or -   des Pro36 [Asp28] Exendin-4(1-39), -   des Pro36 [IsoAsp28] Exendin-4(1-39), -   des Pro36 [Met(O)14, Asp28] Exendin-4(1-39), -   des Pro36 [Met(O)14, IsoAsp28] Exendin-4(1-39), -   des Pro36 [Trp(O2)25, Asp28] Exendin-4(1-39), -   des Pro36 [Trp(O2)25, IsoAsp28] Exendin-4(1-39), -   des Pro36 [Met(O)14 Trp(O2)25, Asp28] Exendin-4(1-39), -   des Pro36 [Met(O)14 Trp(O2)25, IsoAsp28] Exendin-4(1-39), -   wherein the group -Lys6-NH2 may be bound to the C-terminus of the     Exendin-4 derivative;     or an Exendin-4 derivative of the sequence -   des Pro36 Exendin-4(1-39)-Lys6-NH2 (AVE0010), -   H-(Lys)6-des Pro36 [Asp28] Exendin-4(1-39)-Lys6-NH2, -   des Asp28 Pro36, Pro37, Pro38Exendin-4(1-39)-NH2, -   H-(Lys)6-des Pro36, Pro38 [Asp28] Exendin-4(1-39)-NH2, -   H-Asn-(Glu)5des Pro36, Pro37, Pro38 [Asp28] Exendin-4(1-39)-NH2, -   des Pro36, Pro37, Pro38 [Asp28] Exendin-4(1-39)-(Lys)6-NH2, -   H-(Lys)6-des Pro36, Pro37, Pro38 [Asp28] Exendin-4(1-39)-(Lys)6-NH2, -   H-Asn-(Glu)5-des Pro36, Pro37, Pro38 [Asp28]     Exendin-4(1-39)-(Lys)6-NH2, -   H-(Lys)6-des Pro36 [Trp(O2)25, Asp28] Exendin-4(1-39)-Lys6-NH2, -   H-des Asp28 Pro36, Pro37, Pro38 [Trp(O2)25] Exendin-4(1-39)-NH2, -   H-(Lys)6-des Pro36, Pro37, Pro38 [Trp(O2)25, Asp28]     Exendin-4(1-39)-NH2, -   H-Asn-(Glu)5-des Pro36, Pro37, Pro38 [Trp(O2)25, Asp28]     Exendin-4(1-39)-NH2, -   des Pro36, Pro37, Pro38 [Trp(O2)25, Asp28]     Exendin-4(1-39)-(Lys)6-NH2, -   H-(Lys)6-des Pro36, Pro37, Pro38 [Trp(O2)25, Asp28]     Exendin-4(1-39)-(Lys)6-NH2, -   H-Asn-(Glu)5-des Pro36, Pro37, Pro38 [Trp(O2)25, Asp28]     Exendin-4(1-39)-(Lys)6-NH2, -   H-(Lys)6-des Pro36 [Met(O)14, Asp28] Exendin-4(1-39)-Lys6-NH2, -   des Met(O)14 Asp28 Pro36, Pro37, Pro38 Exendin-4(1-39)-NH2, -   H-(Lys)6-desPro36, Pro37, Pro38 [Met(O)14, Asp28]     Exendin-4(1-39)-NH2, -   H-Asn-(Glu)5-des Pro36, Pro37, Pro38 [Met(O)14, Asp28]     Exendin-4(1-39)-NH2, -   des Pro36, Pro37, Pro38 [Met(O)14, Asp28]     Exendin-4(1-39)-(Lys)6-NH2, -   H-(Lys)6-des Pro36, Pro37, Pro38 [Met(O)14, Asp28]     Exendin-4(1-39)-(Lys)6-NH2, -   H-Asn-(Glu)5 des Pro36, Pro37, Pro38 [Met(O)14, Asp28]     Exendin-4(1-39)-(Lys)6-NH2, -   H-Lys6-des Pro36 [Met(O)14, Trp(O2)25, Asp28]     Exendin-4(1-39)-Lys6-NH2, -   H-des Asp28 Pro36, Pro37, Pro38 [Met(O)14, Trp(O2)25]     Exendin-4(1-39)-NH2, -   H-(Lys)6-des Pro36, Pro37, Pro38 [Met(O)14, Asp28]     Exendin-4(1-39)-NH2, -   H-Asn-(Glu)5-des Pro36, Pro37, Pro38 [Met(O)14, Trp(O2)25, Asp28]     Exendin-4(1-39)-NH2, -   des Pro36, Pro37, Pro38 [Met(O)14, Trp(O2)25, Asp28]     Exendin-4(1-39)-(Lys)6-NH2, -   H-(Lys)6-des Pro36, Pro37, Pro38 [Met(O)14, Trp(O2)25, Asp28]     Exendin-4(S1-39)-(Lys)6-NH2, -   H-Asn-(Glu)5-des Pro36, Pro37, Pro38 [Met(O)14, Trp(O2)25, Asp28]     Exendin-4(1-39)-(Lys)6-NH2;     or a pharmaceutically acceptable salt or solvate of any one of the     afore-mentioned Exendin-4 derivative.

Hormones are for example hypophysis hormones or hypothalamus hormones or regulatory active peptides and their antagonists as listed in Rote Liste, ed. 2008, Chapter 50, such as Gonadotropine (Follitropin, Lutropin, Choriongonadotropin, Menotropin), Somatropine (Somatropin), Desmopressin, Terlipressin, Gonadorelin, Triptorelin, Leuprorelin, Buserelin, Nafarelin, Goserelin.

A polysaccharide is for example a glucosaminoglycane, a hyaluronic acid, a heparin, a low molecular weight heparin or an ultra low molecular weight heparin or a derivative thereof, or a sulphated, e.g. a poly-sulphated form of the above-mentioned polysaccharides, and/or a pharmaceutically acceptable salt thereof. An example of a pharmaceutically acceptable salt of a poly-sulphated low molecular weight heparin is enoxaparin sodium.

Antibodies are globular plasma proteins (−150 kDa) that are also known as immunoglobulins which share a basic structure. As they have sugar chains added to amino acid residues, they are glycoproteins. The basic functional unit of each antibody is an immunoglobulin (Ig) monomer (containing only one Ig unit); secreted antibodies can also be dimeric with two Ig units as with IgA, tetrameric with four Ig units like teleost fish IgM, or pentameric with five Ig units, like mammalian IgM.

The Ig monomer is a “Y”-shaped molecule that consists of four polypeptide chains; two identical heavy chains and two identical light chains connected by disulfide bonds between cysteine residues. Each heavy chain is about 440 amino acids long; each light chain is about 220 amino acids long. Heavy and light chains each contain intrachain disulfide bonds which stabilize their folding. Each chain is composed of structural domains called Ig domains. These domains contain about 70-110 amino acids and are classified into different categories (for example, variable or V, and constant or C) according to their size and function. They have a characteristic immunoglobulin fold in which two β sheets create a “sandwich” shape, held together by interactions between conserved cysteines and other charged amino acids.

There are five types of mammalian Ig heavy chain denoted by α, δ, ε, γ, and μ. The type of heavy chain present defines the isotype of antibody; these chains are found in IgA, IgD, IgE, IgG, and IgM antibodies, respectively.

Distinct heavy chains differ in size and composition; α and γ contain approximately 450 amino acids and δ approximately 500 amino acids, while p and E have approximately 550 amino acids. Each heavy chain has two regions, the constant region (CH) and the variable region (VH). In one species, the constant region is essentially identical in all antibodies of the same isotype, but differs in antibodies of different isotypes. Heavy chains γ, α and δ have a constant region composed of three tandem Ig domains, and a hinge region for added flexibility; heavy chains μ and ε have a constant region composed of four immunoglobulin domains. The variable region of the heavy chain differs in antibodies produced by different B cells, but is the same for all antibodies produced by a single B cell or B cell clone. The variable region of each heavy chain is approximately 110 amino acids long and is composed of a single Ig domain.

In mammals, there are two types of immunoglobulin light chain denoted by λ and κ. A light chain has two successive domains: one constant domain (CL) and one variable domain (VL). The approximate length of a light chain is 211 to 217 amino acids. Each antibody contains two light chains that are always identical; only one type of light chain, κ or λ, is present per antibody in mammals.

Although the general structure of all antibodies is very similar, the unique property of a given antibody is determined by the variable (V) regions, as detailed above. More specifically, variable loops, three each the light (VL) and three on the heavy (VH) chain, are responsible for binding to the antigen, i.e. for its antigen specificity. These loops are referred to as the Complementarity Determining Regions (CDRs). Because CDRs from both VH and VL domains contribute to the antigen-binding site, it is the combination of the heavy and the light chains, and not either alone, that determines the final antigen specificity.

An “antibody fragment” contains at least one antigen binding fragment as defined above, and exhibits essentially the same function and specificity as the complete antibody of which the fragment is derived from. Limited proteolytic digestion with papain cleaves the Ig prototype into three fragments. Two identical amino terminal fragments, each containing one entire L chain and about half an H chain, are the antigen binding fragments (Fab). The third fragment, similar in size but containing the carboxyl terminal half of both heavy chains with their interchain disulfide bond, is the crystalizable fragment (Fc). The Fc contains carbohydrates, complement-binding, and FcR-binding sites. Limited pepsin digestion yields a single F(ab′)2 fragment containing both Fab pieces and the hinge region, including the H—H interchain disulfide bond. F(ab′)2 is divalent for antigen binding. The disulfide bond of F(ab′)2 may be cleaved in order to obtain Fab′. Moreover, the variable regions of the heavy and light chains can be fused together to form a single chain variable fragment (scFv).

Pharmaceutically acceptable salts are for example acid addition salts and basic salts. Acid addition salts are e.g. HCl or HBr salts. Basic salts are e.g. salts having a cation selected from alkali or alkaline, e.g. Na+, or K+, or Ca2+, or an ammonium ion N+(R1)(R2)(R3)(R4), wherein R1 to R4 independently of each other mean: hydrogen, an optionally substituted C1 C6-alkyl group, an optionally substituted C2-C6-alkenyl group, an optionally substituted C6-C10-aryl group, or an optionally substituted C6-C10-heteroaryl group. Further examples of pharmaceutically acceptable salts are described in “Remington's Pharmaceutical Sciences” 17. ed. Alfonso R. Gennaro (Ed.), Mark Publishing Company, Easton, Pa., U.S.A., 1985 and in Encyclopedia of Pharmaceutical Technology.

Pharmaceutically acceptable solvates are for example hydrates.

It will be further apparent to those skilled in the art that various modifications and variations can be made to the present invention without departing from the spirit and scope of the invention.

Further, it is to be noted, that any reference numerals used in the appended claims are not to be construed as limiting the scope of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

In the following, a brief description of the drawings is provided, in which:

FIG. 1 schematically illustrates the assembled drive mechanism in a pen-type drug delivery device in a longitudinal cut,

FIG. 2 perspectively illustrates an exploded view of the complete drug delivery device and its various components,

FIG. 3 shows a cross-section along A-A according to FIG. 1,

FIG. 4 shows a cross-section along B-D according to FIG. 1,

FIG. 5 shows a cross-section through the device along C-C according to FIG. 1,

FIG. 6 shows a cross-section through the device along D-D according to FIG. 1,

FIG. 7 shows a cross-section along E-E according to FIG. 1,

FIG. 8 shows a cross-section along F-F according to FIG. 1,

FIG. 9 shows a cross-section along G-G according to FIG. 1,

FIG. 10 shows a cross-section through the device along H-H according to FIG. 1 and

FIG. 11 shows a cross-section along J-J according to FIG. 1,

FIG. 12 shows a longitudinal and enlarged cross section of the drive wheel engaging with the piston rod,

FIG. 13 shows an isolated and perspective illustration of the drive mechanism,

FIG. 14 shows the drive mechanism in a perspective illustration in a longitudinal cross section,

FIG. 15 provides another longitudinal cross section through the drive mechanism,

FIG. 16 shows a partially cut view through a distal end of the drive mechanism,

FIG. 17 shows a perspective and longitudinally cut view of the display assembly,

FIG. 18 shows a longitudinal and magnified cross section through a proximal portion of the display assembly,

FIG. 19 shows a longitudinal and enlarged cross section through a proximal portion of the display assembly,

FIG. 20 shows a partially cut and perspective view of the proximal end of the drug delivery device with a depressed dose dispensing member,

FIG. 21 shows an enlarged view of a proximal end of the drive mechanism according to an alternative embodiment and

FIG. 22 shows a cross-section K-K through the embodiment according to FIG. 21.

DETAILED DESCRIPTION

In FIGS. 1 and 2, the complete drug delivery device 10 is illustrated in a longitudinal cross section cut and in an exploded view. The drug delivery device 10 is of pen-injector type and comprises a substantially cylindrical and axially elongated shape. Throughout the Figures the axial distal direction is denoted with reference number 1 and the opposite proximal direction is denoted with reference number 2. The drug delivery device 10 comprises a drive mechanism 3 having comprising a proximal housing 20 or being assembled in a respective body 20 of the drug delivery device 10.

In distal direction the housing 20 is connected with a cartridge holder 13 which is adapted to accommodate and to receive a cartridge 12 containing the medicament to be dispensed by the drug delivery device 10 by way of its drive mechanism 3. The cartridge 12 typically comprises a vitreous barrel of cylindrical or tubular shape and is sealed in distal direction 1 by a pierceable sealing member, such like a septum.

In proximal direction 2, the cartridge 12 is sealed by means of a piston 14 slidably arranged in the barrel of the cartridge 12. The piston 14 typically comprises an elastomeric material, by way of which the proximal end of the cartridge 12 can be effectively sealed in a fluid-and gas-tight manner. The piston 14 of the cartridge 12 is to be operably engaged with a distal end of a piston rod 160 of the drug delivery device's 10 drive mechanism 3. A distally directed displacement of the piston 14 typically induced and governed by the piston rod 160 leads to a respective build up of a fluid pressure inside the cartridge 12. When the distal outlet of the cartridge 12 is connected with e.g. a needle assembly 16 as illustrated in FIG. 1, a predefined amount of the liquid medicament, which equals a previously set dose of the medicament, can be expelled from the cartridge 12 and can be dispensed via an injection needle 17 of the needle assembly 16.

As illustrated in FIG. 1, the needle assembly 16 comprises the double-tipped injection needle 17. The needle assembly 16 is typically removably arranged on a distal end portion of the cartridge holder 13. Here, a distally located socket of the cartridge holder 13 and the needle assembly 16 comprise mutually corresponding threads to screw the needle assembly 16 onto the cartridge holder 13 in a releasable and removable way.

The cartridge holder 13 and hence the cartridge 12 assembled therein is to be protected and covered by a removable protective cap 19. Prior to setting and/or dispensing of a dose, the protective cap 19 as well as an inner needle cap 18 of the needle assembly 16 have to be removed. After dispensing or injecting of the medicament, e.g. into biological tissue, the needle assembly 17 is typically to be disconnected from the cartridge holder 13 and is to be discarded.

The drive mechanism 3 as illustrated in the various FIGS. 3-19 comprises numerous functional and mechanically inter-engaging components by way of which a dose of variable size can be set and subsequently dispensed. The drive mechanism 3 is of semi-automated type. It comprises a means for storing mechanical energy during a dose setting procedure. Said mechanical energy is then usable for driving the piston rod in distal direction 1 during a dose dispensing procedure. Consequently, it is the device 10 and the drive mechanism 3 that provide mechanical energy and a driving force or driving torque to conduct an injection procedure. Consequently, an injection force does not have to be provided by the user during the dose dispensing process.

Does dispensing requires distally directed advancing of the piston rod 160 relative to the cartridge 12, hence relative to the cartridge holder 13 and relative to the housing 20. The drive mechanism 3 comprises a longitudinally extending hollow shaped drive sleeve 30 that is axially displaceable relative to the housing 20 for switching the drive mechanism 3 between a dose dispensing mode and a dose setting mode. The drive sleeve 30 is rotatably supported on a longitudinal axis 4 that may coincide with the center of the piston rod 160.

The drive sleeve 30 is further connected with a spring element 43 featuring a helical shape and acting as a torsion spring. As illustrated in FIGS. 1 and 4, a distal end 44 of the helical spring element 43 is connected with a distal end portion of the drive sleeve 30 while an opposite, proximal end 45 of the helical spring element 43 is connected to a distal base member 70 as illustrated in FIG. 6. The base member 70 is fastened and unmovably fixed to the housing 20. In embodiments without a base member 70 the proximal end 45 of the helical spring element 43 may also be connected to a portion of the housing 20.

As indicated in FIG. 4 the drive sleeve 30 is rotatable in a dose incrementing direction 5 against the action of the helical spring element 43. For setting of a dose, hence for increasing a dose to be set, the drive sleeve 30 rotates in dose incrementing direction 5, thereby straining and biasing the helical spring element 43. In order to store respective mechanical energy in the drive mechanism 3, the drive sleeve 30 is rotatably engaged with the housing 20 by means of a ratchet member 32. The ratchet member 32 comprises an arc-shaped and resiliently deformable circumferentially extending portion featuring a radially outwardly extending catch portion or protrusion 33 that is adapted to engage with a correspondingly shaped first toothed profile 21 located at an inwardly facing sidewall portion of the housing 20.

As shown in FIG. 4, the catch portion or protrusion 33 of the drive sleeve's 30 ratchet member 32 positively engages with consecutive ratchet teeth 22 of the first toothed profile 21. In this way, the drive sleeve 30 can be rotatably secured to the housing 20 at least when located in its proximal dose setting position. The ratchet member 32 is adapted to prevent a self-actuating rotation of the drive sleeve 30 in dose decrementing direction 6 under the effect of the helical spring element 43.

However, the shape of the ratchet member's 32 catch portion 33 and the shape or slope of the various ratchet teeth 22 are designed such that the drive sleeve 30 may also be rotated in a dose decrementing direction 6 if a respective torque above a predefined threshold is applied to the drive sleeve 30. In this way, a dose correction can be conducted even if the drive sleeve 30 is rotatably secured to the housing 20 by means of the ratchet member 32.

Displacement of the drive sleeve 30 in distal direction 1 disengages the ratchet member 32 from the first tooth profile 21. Consequently, when the drive sleeve 30 is in the distal dose dispensing position it is free to rotate in dose decrementing direction 6 under the effect of the helical spring element 43.

As further illustrated in FIG. 4, the piston rod 160 axially extends through a central and longitudinally extending bore 34 of the drive sleeve 30. The drive sleeve 30 may therefore also act as a linear guide for the piston rod 160.

As further illustrated in FIGS. 13 and 16 the drive sleeve 30 comprises at least one retention spring element 35 at its distal end that is operable to axially engage and to axially abut against a radially inwardly extending flange 25 a of the housing 20. In this way, the drive sleeve 30 is kept in the proximal dose setting position per default. A distally directed displacement of the drive sleeve 30 may therefore act against said at least one retention spring element 35. Bringing and keeping the drive sleeve 30 into the distal dose dispensing position therefore requires to constantly apply a respective thrust or pressure in distal direction 1 to the drive sleeve 30.

A distally directed displacement of the drive sleeve 30 is limited by an axial abutment with a drive wheel 110 that is axially fixed to the housing 20 as illustrated in the cross-section according to FIG. 12. The drive wheel 110 is rotatably supported relative to the housing 20. In particular, the housing 20 comprises a radially inwardly extending guiding portion 27 featuring a central orifice 28 through which the threaded piston rod 160 extends. The piston rod 160 as further illustrated in FIG. 4 comprises two diametrically oppositely located radially inwardly and axially extending grooves 162 that engage with a correspondingly shaped radially inwardly extending protrusion 28 a of the guiding portion 27 as indicated in FIG. 5.

The drive wheel 110 is axially fixed to the housing 20 by means of a positive engagement with a radially inwardly extending fixing member 29 having a radially inwardly extending latch portion to engage with a correspondingly shaped fastening or latch element 116 distally and radially outwardly extending from a distal flange portion 118 of the drive wheel 110. As indicated in FIG. 12, the housing's fixing member 29 is axially constrained between the latch element 116, its radially outwardly extending protrusion 117 and the radially outwardly extending flange portion 118 of the drive wheel 110. In this way, the drive wheel 110 is axially constrained and axially fixed to the housing 20 but may rotate with relative to the housing 20 with the longitudinal or central axis 4 as an axis of rotation.

The mutual engagement of the drive wheel 110 with the fixing member 29 of the housing 20 however allows for a free rotation of the drive wheel 110 at least in a dose decrementing direction 6, as indicated in FIG. 11. As shown there, the drive wheel 110 comprises a circumferentially extending resiliently deformable interlocking member 111 featuring a radially outwardly extending ratchet tooth or protrusion 112 to engage with a second toothed profile 23 of the housing 20. The second toothed profile 23 comprises numerous ratchet teeth 24 radially inwardly protruding from an inward facing sidewall portion of the housing 20. By means of the mutual engagement of the drive wheel's 110 interlocking member 111 with the second toothed profile 23, only a unidirectional rotation of the drive wheel 110, namely in dose decrementing direction 6 is allowed if a respective torque acts on the drive wheel 110.

The ratchet tooth 112 of the interlocking member 111 as well as the shape and design of the various ratchet teeth 24 are designed such, that a dose incrementing rotation of the drive wheel 110 relative to the housing 20 is strictly blocked. In this way, a proximally directed displacement of the piston rod 160 relative to the housing 20 can be effectively prevented.

As it is further indicated in FIG. 12, the piston rod 160 comprises an outer threaded portion 161 threadedly engaged with a correspondingly shaped inner thread 115 of the drive wheel 110. Hence, the drive wheel 110 comprises a central orifice 113 to threadedly engage with the threaded portion 161 of the piston rod. By means of its groove 162 the piston rod 160 is rotatably locked to the housing 20 via the radially inwardly extending protrusions 28 a thereof. If the drive wheel 110 rotates in dose decrementing direction 6 the axial fixing of the drive wheel 110 to the housing 20 and its threaded engagement with the piston rod 160 then leads to a distally directed but non-rotative and hence sliding movement of the piston rod 160.

Consequently, the radially widened pressure foot 163 located at a distal end of the piston rod 160 serves to exert distally directed pressure to the piston 14 for driving the same in distal direction 1 relative to the barrel of the cartridge 12. A rotation of the drive wheel 110 therefore directly transfers into a distally directed displacement of the piston rod 160.

Drive sleeve 30 and drive wheel 110 can be selectively coupled and decoupled to transfer angular momentum therebetween. The drive wheel 110 comprises a crown wheel 114 facing in proximal direction to engage with a correspondingly shaped crown wheel 40 of the drive sleeve 30 provided on a distal end of the drive sleeve 30. By means of displacing the drive sleeve 30 in distal direction 1, hence into its distal dose dispensing position, mutually corresponding crown wheels 40, 114 of drive sleeve 30 and drive wheel 110 mutually engage in a torque transferring way. In this way, a dose decrementing rotation 6 of the drive sleeve 30 can be directly transferred into a respective dose decrementing rotation of the drive wheel 110.

The axial dimensions of mutually corresponding teeth 41, 119 of the drive sleeve's 30 crown wheel 40 and the drive wheel's 110 crown wheel 114 is designed such, that respective crown wheels 40, 114 already engage and rotatably lock even before the drive sleeve 30 reaches the distal dose dispensing position. During a distally directed dose dispensing displacement of the drive sleeve 30 the crown wheels 40, 114 mutually engage before the ratchet member 32 of the drive sleeve 30 disengages from the first toothed profile 21 of the housing 20. In this way, a rather slip-free alternative rotational engagement and rotational disengagement of the drive sleeve 30 with the drive wheel 110 and housing 20 can be achieved.

As in detail illustrated in FIG. 17, a proximal end of the drive sleeve 30 is rigidly connected and fixed to a distal end portion of a dose setting sleeve 50, which in proximal direction 2 extends into or almost through a proximal threaded shaft portion 61 of a proximal base member 60. The dose setting sleeve 50 comprises at least one radially outwardly extending protrusion 57 to engage with a correspondingly shaped indentation or with a respective latch element 42 of the drive sleeve 30. In this way, the dose setting sleeve 50 and the drive sleeve 30 can be rigidly attached in axial direction to transfer a distally directed thrust from the dose setting sleeve 50 towards the drive sleeve 30.

Additionally and as shown in FIG. 6, dose setting sleeve 50 and drive sleeve 30 are also rotatably engaged by mutually corresponding connecting portions. Here, the drive sleeve 30 comprises a non-circular shaped receptacle 39 a to receive a correspondingly shaped connector 53 of the dose setting sleeve 50. In this way also a rotation of the dose setting sleeve 50 unalterably transfers into a respective rotation of the drive sleeve 30.

The drive mechanism 3 further comprises a display assembly 80 which is illustrated in detail in FIGS. 14 and 17. The display assembly 80 comprises a first dose indicating member 81 and a second dose indicating member 82. The dose indicating members 81, 82 comprise a disc-like or sleeve-like shape and both comprise annular display surfaces 86, 87 to visually display variable dose sizes through a window 68 of a cover portion 65 or through a sidewall portion of the housing 20.

The first dose indicating member 81 comprises a first display surface 86 while the second dose indicating member 82 comprises a second annular display surface 87. While the first display surface 86 represents single units of the medicament to be dispensed and therefore comprises numerals from 0-9 the second dose indicating member 82, in particular its display surface 87 comprises numerals from 0, 1, 2, and so on thereby representing decades or tens, such like 10, 20 so on. If the drive mechanism 3 is for instance adapted to set and to inject a maximum dose of insulin of e.g. 120 IU, the numbers present on the second annular display surface 87 range from 1-12.

The two dose indicating members 81, 82 are both rotatably arranged on the longitudinal axis 4 and may be rotated in a dose incrementing direction 5 during dose setting and in an opposite direction, hence in dose decrementing direction 6 during dose dispensing. Accordingly, the numbers showing up in the window 68 either constantly increase or constantly decrease during dose setting and dose dispensing.

Moreover, the first dose indicating member 81 comprises a central orifice 81 a and the second dose indicating member 82 comprises a second central orifice 82 a. Said orifices 81 a, 82 a axially flush and are adapted to receive the dose setting sleeve 50 and/or the drive sleeve 30 as becomes apparent from the sketch of FIG. 17. Even though the assembly of dose setting sleeve 50 and drive sleeve 30 extends through both dose indicating members 81, 82, there is only an indirect transfer of angular momentum between dose setting sleeve 50, drive sleeve 30 and the two dose indicating members 81, 82.

In particular, the first and second dose indicating members 81, 82 are axially fixed relative to the housing 20 and/or relative to the proximal base member 60 and/or to the distal base member 70 as for instance illustrated in FIG. 17. In contrast to that, the assembly of drive sleeve 30 and dose setting sleeve 50 is axially displaceable relative to both dose indicating members 81, 82 for switching the drive mechanism 3 between the dose setting mode and the dose dispensing mode.

In order to transfer a driving torque between dose setting sleeve 50, drive sleeve 30 and at least one of first and second dose indicating members 81, 82 there are provided first and second display wheels 94, 100. As indicated in FIGS. 17 and 7 the dose setting sleeve 50 comprises a first geared portion 54 that meshes with a correspondingly shaped proximally located geared section 96 of the first display wheel 94. Said display wheel 94 further comprises a proximally located pocket hole or receptacle 97 to receive a distally and axially extending pin or bearing 64 of the proximal base member 60.

Distally offset from the proximal geared section 96 the first display wheel 94 further comprises a distal geared section 95 that meshes with a central gear 88 of the first dose indicating member 81. In this way, a dose incrementing or dose decrementing rotation of the dose setting sleeve 50 can be transferred into a respective rotation of the first dose indicating member 81. The first dose indicating member 81 and the second dose indicating member 82 are only indirectly rotatably engaged via the drive sleeve 30 and the dose setting sleeve 50.

Hence, the second dose indicating member 82 is rotatably engaged with the drive sleeve 30 by means of the second display wheel 100. Similar as the first display wheel 94 also the second display wheel 100 is located radially offset from the longitudinal central axis 4 but is located radially inward compared to the display surface 86, 87 of first and/or second dose indicating members 81, 82. Also the second display wheel 100 is rotatably supported on an axially but proximally extending pin or bearing 78 of the distal base member 70 as indicated in FIG. 19. A distally located geared section 101 of the second display wheel 100 meshes with a radially outwardly extending tappet 38 of the drive sleeve 30 as indicated in FIG. 5. In this way, a continuous rotation of the drive sleeve 30 transfers to a discrete and stepwise rotation of the second display wheel 100.

The second display wheel 100 further comprises a proximally located geared section 102 that meshes with a central gear 89 of the second dose indicating member 82.

In the present embodiment according to FIG. 5 the drive sleeve 30 comprises two oppositely located tappets 38. Accordingly, during a complete revolution of the drive sleeve 30, the second dose indicating member 82 is subject to two consecutive discrete stepwise rotations.

By means of first and second display wheels 94, 100 extending parallel to the longitudinal axis 4 and hence parallel to the drive sleeve 30 and dose setting sleeve 50, the dose setting sleeve 50 and the drive sleeve 30 always rotate in the same sense of rotation as the first and second dose indicating members 81, 82.

Moreover and as illustrated in FIG. 17 the first dose indicating member 81 comprises a first annular groove 84 that is open towards the proximal direction 2 while the second dose indicating member 82 comprises a second annular groove 85 that is open towards the distal direction. Both annular grooves 84, 85 are particularly adapted to receive a pin 99, 103 of first and second display wheels 94, 100, respectively. In this way, the distal end of the first display wheel 94 can be radially constrained by the first dose indicating member 81 while a proximal end of the second display wheel 100 can be radially confined by the second dose indicating member 82.

Since the two dose indicating members 81, 82 directly abut in axial direction the first as well as the second dose indicating member 81, 82 can be axially constrained and axially supported by their respective first and second display wheels 94, 100. As indicated in FIG. 18, the first display wheel 94 with its pocket hole 97 axially abuts with the distally extending bearing 64 of the proximally located base member 60. The oppositely located pin 99 is in axial engagement with the annular groove 84 of the first dose indicating member 81. In a corresponding way also the pocket hole 104 of the second display wheel 100 receives the proximally extending bearing 78 of the distal base member 70 thereby supporting the second dose indicating member 82 by means of an axial abutment of its proximal pin 103 with the annular groove 85 of the second dose indicating member 82.

In this way, the first dose indicating member 81 can be axially supported in proximal direction 2 by the first display wheel 94 while the second dose indicating member 82 can be axially supported in distal direction 1 by means of the second display wheel 100. When interconnecting the two base members 60, 70 the first and second dose indicating members 81, 82 mutually abut and are therefore axially constrained and axially fixed relative to first and/or second base members 60, 70. In embodiments, wherein the first and second base members are fixedly attached to the housing 20, first and second dose indicating members 81, 82 are also axially constrained and fixed to the housing 20.

The first and the second display wheels 94, 100 remain permanently engaged with the dose setting sleeve 50 and the drive sleeve 30, respectively. Hence, the axial elongation of the respective geared sections 96, 101 of first and second display wheel 94, 100 allows for a distally directed displacement of drive sleeve 30 and dose setting sleeve 50 for switching the drive mechanism 3 between dose dispensing mode and dose setting mode.

Having a proximal base member 60 and a distal base member 70 allows for an almost complete assembly of the drive mechanism 3 before the drive mechanism 3 in its entirety is inserted into and fixed to the housing 20. As further illustrated in FIG. 15 the distal base member 70 comprises a radially widened receptacle portion 76 at its proximal end to receive and to support the display assembly 80.

Additionally, the display assembly 80 further comprises a third dose indicating member 83 that is axially offset from first and second dose indicating members 81, 82. In the present embodiment as illustrated in FIGS. 13 and 17 the third dose indicating member 83 also comprises an annular shape and features a third display surface 92 that is discernable through another window 67 of the cover portion 65 of the proximal base member 60. The third display surface 92 features a symbol or a color to visually indicate to the user whether the device 10 is in an idle state and is ready for setting of a dose or whether a dose setting or dose dispensing process is actually in progress.

The third dose indicating member 83 comprises a geared rim 91 on its inside facing sidewall portion that is adapted to engage with a radially outwardly extending tappet 98 of the first display wheel 94 as indicated in FIG. 9. The tappet 98 is located axially between the distal geared section 95 and the proximal geared section 96 of the first display wheel.

The second as well as the third display wheel 82, 83 further comprise or interact with a retaining structure for keeping the respective dose indicating member 82, 83 in a particular rotational position when the tappet 98 of the first display wheel 94 and hence the tappet 38 of the drive sleeve 30 is actually disengaged from the retaining structure 93 or from the geared section 101 of the display wheel 100. As illustrated in FIGS. 1 and 9 the proximal base member 60 comprises a distally extending retaining member 69 of pin-like shape and featuring a radially outwardly extending bulged portion to engage with a correspondingly shaped recess 93 a of the third dose indicating member's 83 retaining structure 93.

The circumferential distance of adjacent recesses 93 a corresponds to the mutual engagement of the geared rim 91 and the tappet 98. In this way, discrete and stepwise rotation of the third dose indicating member 83 always starts and ends with a mutual engagement of the retaining member 69 with the retaining structure 93. In this way, the third dose indicating member 83 can be rotatably secured to the base member 60 and hence to the housing 20 if the tappet 98 even when the first display wheel 94 is disengaged from the geared rim 91 of the third dose indicating member 83.

In a similar way also the second dose indicating member 82 can be rotatably secured to the distal base member 70. As indicated in FIGS. 5 and 6, the base member 70 comprises a radially outwardly extending annular shaped retaining structure 72 featuring various radially outwardly but circumferentially spaced protrusions 73. As shown in FIGS. 5 and 6, the second dose indicating member 82 comprises a correspondingly shaped inside facing recessed structure with numerous recesses 87 a that correspond and engage with the radially outwardly extending protrusion 73 of the base member 70. Also here, the mutually corresponding recesses 87 a and protrusions 73 serve to provide a stepwise and consecutive securing or engagement of the second dose indicating member 82 with the base member 70.

From the sketches of FIGS. 5, 7 and 14 also the mutual assembly of the proximal base member 60 with the housing 20 becomes apparent. The housing 20 comprises a longitudinally extending slot or recess 26 at its proximal end to receive the cover portion 65 of the proximal base member 60. At circumferential side edges of the recess 26 the housing 20 comprises radially inwardly located prongs 25 extending from opposite sides at least partially into the recess 26 in tangential or circumferential direction. Here, the prongs 25 provide a radial support structure for the cover portion 65. Additionally, the prongs 25 extend radially inwardly from the inner sidewall of the housing 20 and may therefore engage with a correspondingly shaped recess 75 of an arc-shaped fixing portion 79 of the distal base member 70.

By means of this positive engagement the proximal as well as the distal base members 60, 70 can be rotatably fixed to the housing 20. Moreover, as illustrated in FIG. 14 the proximal base member 60 comprises at least one distally extending and radially deformable fastening element 63 by way of which the proximal base member 60 can be axially fixed to the housing 20. In particular, the proximal base member 60 can be clipped to the housing 20 while the distal base member 70 may axially abut against a radially stepped or recessed portion of the housing 20.

As shown in detail in FIGS. 14 and 15 the proximal base member 60 comprises a proximal shaft portion 61 featuring an outer thread 62. Additionally and radially offset from said shaft portion 62, the proximal base member 60 comprises a radially inwardly extending flange portion 66 adapted to engage with a fastening element 125 of a dose setting member 120. As indicated in FIG. 14, the sleeve-shaped dose setting member 120 comprises a latch-like radially resiliently deformable fastening element 125 to engage with the indentation formed by the radially inwardly extending flange portion 66 of the proximal base member 60. In this way, the dose setting member 120 can be axially fixed to the base member and may freely rotate relative to the base member.

Additionally, there is provided a cup-shaped dose dispensing member 130. Said dose dispensing member 130 may be permanently rotatably engaged with the sleeve like dose setting member 120 as becomes apparent from the cross-section according to FIG. 3. The dose dispensing member 130 acting as a dose button comprises an axially extending shaft portion 132 extending towards a proximal end of a proximal sleeve portion 51 of the dose setting sleeve 50 extending through the hollow proximal shaft portion 61 of the proximal base member 60.

The dose setting member 120 comprises an annular cross-section featuring various grip structures 127 at its outer surface. The dose setting member 120 further comprises various radially inwardly extending protrusions 124 extending into circumferentially extending arched portions 121, 121 a, 121 b as illustrated in FIG. 3. Here, the protrusions 124 may act as bridging portions for integrally connecting the inner arched portion 121 with the outer sleeve portion of the dose setting member 120. Between arched portions 121 a, 121 b there is formed an axially extending slot or recess 123 to receive a radially outwardly extending protrusion 141 of a last dose limiting member 140.

As indicated in FIGS. 3 and 14 said last dose limiting member 140 is radially sandwiched between the proximal base member 60, in particular between its proximal shaft portion 61 and the dose setting member 120. The last dose limiting member 140 comprises an inner thread 142 threadedly engaged with the outer thread 62 of the proximal base member 60. In this way, the annular shaped last dose limiting member 140 is subject to a rotation relative to the base member 60 when the dose setting member 120 is dialled either in a dose incrementing direction 5 or dose decrementing direction 6 s.

Due to the axially elongating recess 123 of the dose setting member 120 the last dose limiting member 140 is allowed to travel in axial direction as the dose setting member 120 is rotated.

The last dose limiting member 140 further comprises a radial stop 143 to engage with a correspondingly shaped radial stop 61 a of the base member 60 when reaching an end-of-content configuration which is illustrated in FIG. 20.

As illustrated in detail in FIG. 15, the dose dispensing member 130 extends with a sidewall portion 135 between the inner arched portions 121, 121 a, 121 b of the dose setting member 120 and the outer sidewall portion 128 of the dose setting member 120. Moreover, and as illustrated in FIG. 15 the dose dispensing member 130 comprises at least one or several axially extending spring elements 136 to abut against a bottom portion 129 of the dose setting member 120. Said bottom portion 129 may radially extends between and may connect the arched portions 121 with the radially outwardly located sidewall portion 128 of the dose setting member 120.

In this way the dose dispensing member 130 can be axially displaced in distal direction 1 relative to the dose setting member 120 against the action of the at least one spring element 136. This spring element 136 is of particular use to bring and to transfer the dose dispensing member 130 into a proximal dose setting configuration as for instance illustrated in FIG. 15.

For transferring the drive mechanism 3 from the dose setting mode into the dose dispensing mode a user simply depresses the dose dispensing member 130 in distal direction 1. Then, the shaft portion 132 thereof axially abuts with a proximal end of the dose setting sleeve 50 thereby displacing the dose setting sleeve 50 in distal direction 1. Since the dose setting sleeve 50 is axially rigidly connected with the drive sleeve 30 also the drive sleeve 30 experiences a respective distally directed displacement until it reaches the distal dose dispensing configuration, in which the drive sleeve 30 is liberated from the housing 20 and in which the drive sleeve 30 is free to rotate under the action of the helical spring element 43.

Moreover, by displacing the dose dispensing member 130 in distal direction 1 a geared portion 131 of the axially extending shaft portion 132 of said dose dispensing member 130 is adapted to rotatably lock to the proximal base member 60, thereby inhibiting a potential rotation of the dose dispensing member 130 relative to the base member 60 or relative to the housing 20.

Since the dose dispensing member 130 is permanently rotatably locked to the dose setting member 120 by the radially inwardly extending protrusions 124 extending through respective recesses or slots 133 of the dose dispensing member 130 also the dose setting member 120 is rotatably locked to the base member 60 when the dose setting member 120 is in its distal dose dispensing position. Due to the rotational interlocking of the dose setting member 120 relative to the base member 60 the dose setting member 120 cannot rotate during a dose dispensing procedure. In this way also the last dose limiting member 140 cannot be rotated or axially displaced during a dose dispensing procedure.

Moreover, as indicated in FIG. 15 the dose setting member 120 comprises a radially inwardly extending flange portion 126 at its proximal end featuring a central through opening with a radially inwardly extending geared structure 126 a. Said geared structure 126 a is rotatably engaged with a correspondingly shaped geared portion 56 of the proximal sleeve portion 51 of the dose setting sleeve 50. When located in proximal dose setting position the dose setting sleeve 50 is hence rotatably locked or rotatably engaged with the dose setting member 120. A rotation of the dose setting member 120 relative to the base member 60 therefore leads to a respective rotation of the dose setting sleeve 50 and hence to a respective rotation of the drive sleeve 30.

By displacing the dose dispensing member 130 in distal direction 1 and by correspondingly displacing the dose setting sleeve 50 in its distal dose dispensing position the dose setting sleeve 50 is operably disengaged from the dose setting member 120. At the same time, or even prior to the disengagement of dose setting sleeve 50 and dose setting member 120 the dose dispensing member 130 rotatably locks to the proximal base member 60.

In this way the dose setting member 120 is only rotatable when the drive mechanism 3 is in dose setting mode. Due to the decoupling of the dose setting sleeve 50 from the dose setting member 120 during a dose dispensing the axial position of the last dose limiting member 140 reflects the sum of doses consecutively set and dispensed by the drive mechanism.

In the following setting of a dose if described.

For setting of a dose a user simply dials the dose setting member 120 in dose incrementing direction 5. Due to its rotational engagement with the dose setting sleeve 50 also said dose setting sleeve 50 together with the drive sleeve 30 are rotated accordingly against the action of the helical spring element 43. Said rotational displacement is secured by the drive sleeve's 30 ratchet member 32. Here, the ratchet member 32 provides an audible feedback to the user as it meshes along consecutive radially inwardly extending teeth 22 of the first toothed profile 21 of the housing 20. Since the ratchet member 32 is resiliently deformable it is operable to generate a click sound when rotated relative to the teeth 22 of the first toothed profile 21. Additionally, at least the first dose indicating member 81 as well as the third dose indicating member 83 are rotated in a dose incrementing way, thereby illustrating to the user the size of the dose actually set.

Moreover, and as becomes apparent from FIGS. 10 and 15, there is a provided a single dose limiting member 150 disposed radially between the drive sleeve 30 and the distal base member 70. Here, the arc-shaped or semicircular-shaped single dose limiting member 150 comprises a radially outwardly extending protrusion 151 engaged with a correspondingly radially outwardly extending and axially elongated recess 71 of a distal sleeve portion 74 of the base member 70. In this way, the single dose limiting member 150 is rotatably locked to the stationary base member 70 and may only slide along the axially extending groove or recess 71 thereof during a dose incrementing or a dose decrementing rotation 5, 6 of the drive sleeve 30.

Additionally and as illustrated in FIG. 15 the drive sleeve comprises an outer threaded portion 31 engaged with an inner thread 152 of the single dose limiting member 150. It is due to the keyed or splined engagement of the single dose limiting member 150 with the distal base member 70 and due to the threaded engagement of the single dose limiting member 150 with the drive sleeve 30 that a rotation of the drive sleeve 30 transfers to an axial displacement of the single dose limiting member 150. The single dose limiting member 150 comprises at least one radial stop 154, 155, e.g. at its circumferential end to engage with a correspondingly shaped radial stop 36 of the drive sleeve 30, e.g. located near a distal end of its threaded portion 31. As the drive sleeve 30 is dialled and rotated in dose incrementing direction 5 the single dose limiting member 150 may advance in distal direction 1 until it engages with the distal stop 36 of the drive sleeve 30.

When mutually corresponding radial stop faces 155 and radial stop 36 get in direct abutment a further rotation of the drive sleeve 30 is effectively blocked due to the splined or keyed engagement of the single dose limiting member 150 with the distal base member 70. The axial position of the stop 36 as well as the lead of the threaded engagement of the single dose limiting member 150 and the drive sleeve 30 is adapted such that such a blocking configuration correlates to a maximum allowable dose size, of e.g. 120 IU of insulin.

The oppositely located radial stop 154 of the single dose limiting member 150 may act as a zero dose stop adapted to engage with another radial but proximally located stop 37 of the drive sleeve 30. Mutual engagement of the radial stop 154 of the single dose limiting member 150 with the proximally located stop 37 of the drive sleeve 30 effectively inhibits that a user may set a negative dose.

Additionally, the single dose limiting member 150 further comprises a resiliently deformable clicking member 153 that may at least occasionally audibly engage with the stop 37 of the drive sleeve 30 as the single dose limiting member 150 approaches a zero dose configuration, in particular when a dose dispensing procedure terminates. In this way, an audible feedback can be provided to a user that the drive mechanism 3 returns into an initial state. The clicking member is typically axially deformable and may therefore audibly engage the stop 37 drive sleeve 30 radially outwardly extending therefrom.

Since the single dose limiting member 150 is permanently threadedly engaged with the drive sleeve 30 it moves forth and back as the drive sleeve 30 is rotated in dose incrementing direction 5 during dose setting and as the drive sleeve 30 is rotated in the opposite, dose decrementing direction 6 during dose dispensing or dose correction.

After a dose of intended size has been set the drive mechanism 3 and hence the drug delivery device 10 is ready for dispensing of said dose.

In the following dispensing of a dose is described

The dispensing procedure is started by depressing the dose dispensing member 130 in distal direction 1. Then, the dose dispensing member 130 rotatably locks to the proximal base member 60 and therefore also locks a rotation of the dose setting member 120 relative to the proximal base member 60. As shown in FIG. 20 the dose dispensing member 130 comprises a distally extending pin 131 a to engage with a correspondingly shaped recessed structure (not illustrated) of the proximal base member 60. When depressing the dose dispensing member 130 in distal direction it rotatably locks to the proximal base member 60 by means of the pin 131 a, thereby also impeding a further rotation of dose setting member 120 when the device 10 is in dose dispensing mode. By means of this kind of interlocking misuse of the device, hence dialling of the dose setting member during dose dispensing is effectively prevented.

The axial position of the last dose limiting member 140 is then fixed at least during the duration of the dose dispensing procedure. Additionally, the distally extending shaft portion 132 axially abuts with the dose setting sleeve 50 and drives the dose setting sleeve 50 out of engagement from the dose setting member 120. Since the axial displacement of the dose setting sleeve 50 is directly and unalterably transferred to the drive sleeve 30 the drive sleeve 30 will engage with its crown wheel 40 with the correspondingly shaped crown wheel 114 of the drive wheel 110.

After or as soon as a torque transmitting coupling of drive sleeve 30 and drive wheel 110 is established the ratchet member 32, e.g. integrally formed with the drive sleeve 30, also disengages from the first toothed profile 21 of the housing 20, thereby liberating and releasing the rotation of the drive sleeve 30. Consequently, the drive sleeve 30 and hence the drive wheel 110 start to rotate in the dose decrementing direction 6 under the effect of the helical spring element 43 previously strained and biased during dose setting.

As already described, not only the piston rod 160 is driven in distal direction 1 by the revolutions of the drive wheel 110 but also the single dose limiting member 150 returns into its initial position until its radial stop 154 engages with a corresponding radial stop 37 of the drive sleeve. Additionally, the clicking element 153 audibly engages with the stop 37 of the drive sleeve in order to audibly indicate to a user that a dose dispensing procedure just terminated.

During the entire dose injection or dose dispensing process it is required that the user keeps the dose dispensing member 130 depressed against the action of the retention spring element 35 of the drive sleeve 30. When releasing the dose dispensing member 130 the drive sleeve 30 as well as the dose setting sleeve 50 interconnected therewith return into their proximal dose setting position which is e.g. characterized by a radially outwardly extending flange portion 46 of the drive sleeve 30 that axially abuts with a correspondingly shaped radially inwardly extending flange portion 77 of the distal base member 70 as illustrated for instance in FIG. 15. This proximally directed displacement of the drive sleeve 30 and the dose setting sleeve 50 also disengages the rotational interlock of the dose dispensing member 130 and the proximal base member 60. As a consequence, the dose setting member 120 may be repeatedly rotated for setting of a consecutive dose.

As it becomes further apparent from FIG. 11 a dose decrementing rotation of the drive wheel 110 during a dose dispensing procedure is typically accompanied by the interlocking member 111 meshing with the ratchet teeth 24 of the second toothed profile 23. Dose decrementing rotation of the drive wheel 110 is therefore accompanied with an audible feedback, e.g. in form of a clicking noise indicating to a user of the device 10 that a dose dispensing procedure is actually in progress.

In FIGS. 21 and 22 an alternative embodiment is illustrated, wherein the last dose limiting member 240 only comprises a semi-circular, arched shape with oppositely located radial stop portions 243 a, 243 b to engage with correspondingly shaped radial stop portions of the proximal base member 260. Also here, the proximal base member 260 comprises a proximally extending shaft portion 261 featuring an outer thread 262 to engage with an inner thread 242 of the last dose limiting member 240. The dose setting member 220 comprises a recess 223 at its inside facing sidewall portion 228 to receive the radially outwardly extending protrusion 241 of the last dose limiting member 240.

Also here, the dose dispensing member 230 comprises a distally extending shaft portion 231 to apply distally directed thrust to the co-aligned dose setting sleeve 50. The sidewall portions 235 and 228 of the dose dispensing member 230 and the dose setting member 220 are rotatably engaged, e.g. by mutually corresponding radially extending protrusions and recesses, that are not particularly illustrated here. In this way also a permanent rotational interlock of dose setting member 220 and dose dispensing member 230 can be attained.

For rotatably securing or rotatably interlocking the dose dispensing member 230 to the base member 260 the dose dispensing member 230 comprises a stepped portion 233 that may either comprise a crown wheel or radially outwardly extending gears to rotatably lock to the proximal base member 260 when distally displaced in dose dispensing position.

Additionally, there is provided a sleeve-shape transfer element 210 that serves as a torque transmitting coupling member between the dose setting sleeve 50 and the shaft portion 232 of the dose dispensing member 230. In the embodiment according to FIGS. 20 and 21 a user induced rotation of the outer dose setting member 220 is first transferred to a respective rotation to the dose dispensing member 230 and is then transferred via the dose dispensing member 230 and its distally extending shaft portion 232 via the transfer element 210 to the dose setting sleeve 50. By distally displacing the dose dispensing member 230 for dose dispensing the dose setting sleeve 50 is advanced and pushed in distal direction so as to disengage from the geared transfer element 210.

LIST OF REFERENCE NUMERALS

-   1 distal direction -   2 proximal direction -   3 drive mechanism -   4 longitudinal axis -   5 dose incrementing direction -   6 dose decrementing direction -   10 drug delivery device -   12 cartridge -   13 cartridge holder -   14 piston -   16 needle assembly -   17 injection needle -   18 needle cap -   19 protective cap -   20 housing -   21 toothed profile -   22 ratchet tooth -   23 toothed profile -   24 ratchet tooth -   25 prong -   25 a flange portion -   26 recess -   27 guiding portion -   28 orifice -   28 a protrusion -   29 fixing member -   30 drive sleeve -   31 threaded portion -   32 ratchet member -   33 catch portion -   34 bore -   35 spring element -   36 stop -   37 stop -   38 tappet -   39 a receptacle -   40 crown wheel -   41 crown tooth -   42 latch element -   43 spring element -   44 distal end -   45 proximal end -   46 flange portion -   50 dose setting sleeve -   51 sleeve portion -   52 shaft portion -   53 connector -   54 geared portion -   56 geared portion -   57 protrusion -   60 base member -   61 shaft portion -   61 a—radial stop -   62 outer thread -   63 fastening element -   64 bearing -   65 cover portion -   66 flange portion -   67 window -   68 window -   69 retaining member -   70 base member -   71 recess -   72 retaining structure -   73 protrusion -   74 sleeve portion -   75 recess -   76 receptacle -   77 flange portion -   78 bearing -   79 fixing portion -   80 display assembly -   81 dose indicating member -   81 a central orifice -   82 dose indicating member -   82 a central orifice -   83 dose indicating member -   84 annular groove -   85 annular groove -   86 display surface -   87 display surface -   87 a recess -   88 central gear -   89 central gear -   91 geared rim -   92 display surface -   93 retaining structure -   93 a recess -   94 display wheel -   95 geared section -   96 geared section -   97 pocket hole -   98 tappet -   99 pin -   100 display wheel -   101 geared section -   102 geared section -   103 pin -   104 pocket hole -   110 drive wheel -   111 interlocking member -   112 ratchet tooth -   113 orifice -   114 crown wheel -   115 inner thread -   116 latching element -   117 protrusion -   118 flange -   119 crown tooth -   120 dose setting member -   121 arched portion -   121 a arched portion -   121 b arched portion -   123 recess -   124 protrusion -   125 fastening element -   126 flange portion -   126 a geared structure -   127 gripping structure -   128 sidewall -   129 bottom portion -   130 dose dispensing member -   131 geared portion -   131 a pin -   132 shaft portion -   133 slot -   134 proximal end phase -   135 sidewall -   136 spring element -   140 last dose limiting member -   141 protrusion -   142 inner thread -   143 radial stop -   150 single dose limiting member -   151 protrusion -   152 thread -   153 clicking element -   154 radial stop -   155 radial stop -   160 piston rod -   161 threaded portion -   162 groove -   163 pressure foot -   210 transfer element -   220 dose setting member -   223 slot -   228 sidewall portion -   230 dose dispensing member -   231 geared portion -   232 shaft portion -   233 stepped portion -   235 sidewall portion -   240 last dose limiting member -   241 protrusion -   242 inner thread -   243 a radial stop -   243 b radial stop -   260 base member -   261 shaft portion -   262 outer thread 

The invention claimed is:
 1. A drive mechanism of a drug delivery device for dispensing of a dose of a medicament, the drive mechanism comprising: an elongated housing extending in an axial direction; a piston rod to operably engage with a piston of a cartridge to displace the piston in an axial distal direction; a dose setting member rotatably arranged at a proximal end of the housing for setting of a dose; a base member having a proximally extending shaft portion at least partially enclosed by the dose setting member; and a last dose limiting member radially disposed between the dose setting member and the base member, the last dose limiting member directly engaged with the dose setting member, the last dose limiting member having at least one radial stop to limit a rotational displacement of the dose setting member relative to the base member, wherein the last dose limiting member is rotatably locked and axially displaceable to one of the base member or the dose setting member, and wherein the last dose limiting member is threadedly engaged with the other one of the base member or the dose setting member.
 2. The drive mechanism according to claim 1, wherein the last dose limiting member comprises a radial protrusion engaged with a correspondingly shaped radial and axially extending recess of the dose setting member or base member or wherein the last dose limiting member comprises a radial and axially extending recess engaged with a correspondingly shaped radial protrusion of one of the dose setting member or the base member.
 3. The drive mechanism according to claim 2, wherein the last dose limiting member comprises a radially outwardly extending protrusion extending into or through a radial recess of the dose setting member and wherein the last dose limiting member comprises an inner thread engaged with an outer thread of the base member.
 4. The drive mechanism according to claim 1, wherein the radial stop of the last dose limiting member is provided to engage with a corresponding radial stop of the base member.
 5. The drive mechanism according to claim 1, wherein the last dose limiting member comprises an annular structure and wherein the radial stop extends in axial direction from said annular structure to engage with a corresponding radial stop of the dose setting member or base member.
 6. The drive mechanism according to claim 1, further comprising a dose setting sleeve rotatably and axially connected with a drive sleeve and being axially displaceable between a proximal dose setting position and a distal dose dispensing position.
 7. The drive mechanism according to claim 1, wherein the base member is integrally formed with the housing or wherein the base member is fixed in or to the housing.
 8. The drive mechanism according to claim 6, wherein the dose setting member is rotatably engaged with the dose setting sleeve when in the dose setting position and wherein the dose setting member is rotatably disengaged from the dose setting sleeve when in the dose dispensing position.
 9. The drive mechanism according to claim 6, further comprising a dose dispensing member arranged at a proximal end of the dose setting member and being depressible in the distal direction for displacing the dose setting sleeve in the dose dispensing position.
 10. The drive mechanism according to claim 9, wherein the dose dispensing member comprises an axially extending shaft portion extending from a proximal end face and adapted to axially abut with the dose setting sleeve.
 11. The drive mechanism according to claim 9, wherein the dose setting member and the dose dispensing member are rotatably engaged by at least one radially inwardly extending protrusion of the dose setting member extending through an axially extending slot of the dose dispensing member.
 12. The drive mechanism according to claim 11, wherein the dose setting member comprises at least two circumferentially separated radially inwardly extending protrusions extended by a circumferentially extending arched portion.
 13. The drive mechanism according to claim 12, wherein a radial recess of the dose setting member is engaged with a protrusion of the last dose limiting member that is located in the arched portion or between adjacently located arched portions facing towards each other.
 14. The drive mechanism according to claim 9, wherein the dose dispensing member is rotatably locked to the base member when distally displaced in the dose dispensing position.
 15. The drive mechanism according to claim 9, wherein the dose setting sleeve is rotatably locked to the dose setting member when in the dose setting position and wherein the dose setting sleeve is decoupled from the dose setting member when in the distal dose dispensing position.
 16. The drive mechanism according to claim 9, wherein the dose setting member is rotatably locked to the base member via the dose dispensing member when in the dose dispensing position.
 17. A drug delivery device for dispensing of a dose of a medicament, comprising: a drive mechanism comprising: an elongated housing extending in an axial direction; a piston rod to operably engage with a piston of a cartridge to displace the piston in an axial distal direction; a dose setting member rotatably arranged at a proximal end of the housing for setting of a dose; a base member having a proximally extending shaft portion at least partially enclosed by the dose setting member; and a last dose limiting member radially disposed between the dose setting member and the base member, the last dose limiting member directly engaged with the dose setting member, the last dose limiting member having at least one radial stop to limit a rotational displacement of the dose setting member relative to the base member, wherein the last dose limiting member is rotatably locked and axially displaceable to one of the base member or the dose setting member, and wherein the last dose limiting member is threadedly engaged with the other one of the base member or the dose setting member; and a cartridge at least partially filled with the medicament and being arranged in the housing of the drive mechanism or in a cartridge holder fixed to the housing.
 18. The device according to claim 17, wherein the last dose limiting member comprises a radial protrusion engaged with a correspondingly shaped radial and axially extending recess of the dose setting member or base member or wherein the last dose limiting member comprises a radial and axially extending recess engaged with a correspondingly shaped radial protrusion of one of the dose setting member or the base member.
 19. The device according to claim 17, wherein the last dose limiting member comprises a radially outwardly extending protrusion extending into or through a radial recess of the dose setting member and wherein the last dose limiting member comprises an inner thread engaged with an outer thread of the base member.
 20. A method of dispensing a dose of a medicament using a drug delivery device, the method comprising: engaging a piston rod of a drive mechanism of the drug delivery device with a piston of a cartridge at least partially filled with the medicament, the cartridge connected to a housing of the drive mechanism; setting a dose of the medicament using a dose setting member rotatably arranged at a proximal end of the housing, wherein a base member of the drive mechanism having a proximally extending shaft portion is at least partially enclosed by the dose setting member; displacing the piston in the axial distal direction causing a displacement that rotationally displaces the dose setting member relative to the base member, the displacement dispensing the dose of the medicament; and limiting a rotational displacement of the dose setting member relative to the base member using a last dose limiting member radially disposed between the dose setting member and the base member, the last dose limiting member directly engaged with the dose setting member, wherein the last dose limiting member is rotatably locked and axially displaceable to one of the base member or the dose setting member, and wherein the last dose limiting member is threadedly engaged with the other one of the base member or the dose setting member. 